• Category
  • Length Range
    18-71 µm
  • Width Range
    8.5-14 µm
  • Striae in 10 µm
  • Reported As
    Surirella minuta (Krammer and Lange-Bertalot 1987)



Valve length to width ratio is between 2 and 5. The keel is low and alar canals are not visible. The headpole is slightly broader and rounder than the footpole. Apices are broadly rounded and the valve sides are straight,tapering slightly toward the footpole. Fibulae 9-12 in 10 μm, extending from the mantle to the midline. Costae are fine, 25-32 in 10 µm, extending from the valve margin to the midline. Every third or fourth costa is raised, 6-9 in 10 µm. Between the costae there are 3-5 rows of areolae only visible with SEM.


This taxon cam be confused with S. minuta and S. lacrimula and the records shown on this page may include all three species. Records of S. minuta in North America are uncertain and specimens should be carefully examined. These taxa are more abundant in streams that have been more impacted by increased amounts of fine sediments and nutrients.

Original Description

  • Author
    W.Smith 1853
  • Length Range
    15-33 µm

Original Images

Suripinnata Orig Ill
Suripinnata Orig Descr


May 10, 2020 - Clarification of identity

From February 2011 to May 2020, this page appeared as Surirella minuta. English and Potapova (2012) examined the type material of both S. pinnata and S. minuta, and concluded that that specimens illustrated on this page belong to S. pinnata as they possess the long fibulae characteristic of S. pinnata. The name of the page was revised to reflect our revised understanding of the species. - M. Potapova

Cite This Page

English, J. (2011). Surirella pinnata. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/surirella_pinnata


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Surirella pinnata from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.